The present invention relates to a gate valve for use in closing and opening fluid flow through a pipeline having a large diameter or nominal width, particularly a pipeline having passing therethrough a high temperature fluid such as hot blast. The present invention particularly is directed to such a gate valve including an air cooled housing and a damper or valve member movable therein between closed and open positions, the housing and valve member having surfaces or seats which cooperate in the closed position of the valve member to form air tight seals, there being a cooling gap in the area of the air seal seat of the housing that opens into the interior of the housing.
A gate valve of this general type is disclosed in West German DE-OS No. 30 11 369 and includes a cooling gap formed by a spring-loaded auxiliary frame in the valve gate housing that cooperates with corresponding sealing strips or with a supplementary joint ring of the valve member. This arrangement however results in a very complex gate valve design, not only because of the necessary auxiliary frame and sealing strips coacting therewith, but also due to the considerable amount of space required by these supplementary components. Additionally, this known arrangement has the drawback that the cooling air flowing through the cooling gap must be injected into the hot blast pipeline of the hot blast furnace, even if the plant is shut down, in order to prevent overheating as a result of radiation from refractory materials. This leads to an undesirable cooling of the refractory elements, and also makes repair work on the pipeline impossible. An even further disadvantage of this known arrangement is the fact that the main heat load is applied to the so-called "six o'clock" angular area of the gate valve, i.e. that area thereof which is first opened upon movement of the valve member from the closed position to the open position. Due to the differential pressure that arises when the valve member is initially moved from the closed position toward the open position, the hot gas flows at high velocity through the crescent-shaped gap that first forms in such "six o'clock" angular area. This often leads to thermal shock, thereby resulting in damage to the gate valve.